1. Field of the Invention
This invention relates to a brushless alternator, and more particularly to the shape of a plate constituting a bobbin, and a joint structure of the plate and a yoke.
2. Description of the Related Art
A related art brushless alternator has a bobbin for a field coil, and a cylindrical portion of a plate is fitted around a stepped portion of a yoke constituting the bobbin so that one end of the cylindrical portion closely contacts the stepped portion. (Refer to, for example, JP-A-2005-80440)
The brushless alternator disclosed in JP-A-2005-80440 merely shows that the size of a radial height-reduced section of the stepped portion is slightly larger than the thickness of the cylindrical portion of the plate in the radial direction thereof. In this portion, a flow of a magnetic flux was not smooth, and the efficiency of a magnetic circuit could not be improved.